Bit assemblies are utilized in road, off-road and mining machinery on the perimeter and across the width of a rotary drum or on the outside of a continuous chain or the like where the bits are moved through an orbit which is intercepted by the face of the material being removed or recycled. Road milling equipment removes the defective surface of a road and smoothes the top of all or selected portions of the road surface. The bits utilized include a tip and a shank. The shank is received and may axially rotate in a bit holder which is secured onto a bit block that, in turn, is mounted on the drum. Each of the bits has a hardened tip, preferably made of tungsten carbide or such other hardened material that acts to remove a portion of the surface it contacts. By using a sufficient number of these bits around the outer surface of a rotating drum, a large amount of surface may be worked.
The bit assembly including the bit, bit holder and bit block, act on the portion of the surface it is removing to separate that surface from the underlayment and as the drum rotates, passed that surface over the outside of the bit assembly. The milling of concrete and macadam surfaces required a substantial power output to operate the drum or continuous chain or the like. With the use of such a substantial power output to operate the heavy milling machinery, a need has developed to provide a more efficient bit assembly that utilizes less power to perform the same function as machines fitted with prior art bit assemblies.
In O'Neill et al, U.S. Pat. No. 4,915,455, a substantially frustoconical bit is mounted upon a block that provides a large mostly flat forward leading surface that impedes the flow of macadam or concrete therearound and provides a barrier to movement of the bit on additional portions of the surface to be milled.
Additionally, a need has developed for providing ease of removability of bit holders in their bit blocks, especially when portions of or all of the assembly becomes worn and in need of replacement. U.S. Pat. No. 5,374,111 discloses an undercut flange at the bottom of a base of a bit that allows a pry bar to be wedged between that flange and the top of the bit block to help remove a bit from the bit block. It would be desirable to provide more efficient means and multiple means for allowing the removal of a bit holder from a bit block. Additionally, heretofore known bit holders have been retained in bit blocks by the use of threaded nuts or retainer rings. A need has developed to provide means to mount the shank portion of a bit holder in a bit block without the need of a fastener on the distal end of the bit holder shank to retain same in the bit block.
Further, a need has developed for a truly quick-change type of bit holder that may easily and quickly be inserted in the bit block and removed therefrom.
It is, therefore, an object of the present invention, generally stated, to provide an improved means for quickly mounting and/or removing a bit holder from its associated bit block.
Another object of the present invention is the provision of a more efficient bit assembly that requires less power to run when mounted on road milling equipment than heretofore known bit assemblies while providing longer lasting useful life of operation.
A further object of the present invention is the provision of multiple means for retaining a bit holder in a bit block by means of a resilient interference fit between the holder and the block.
Another object of the present invention is the provision of an easily mounted tool on the bit holder that facilitates the removal of the bit holder from the bit block at the front of the leading surface of the bit holder without the need for a large amount of access to the rear of the bit block.